I asked this question yesterday on English Language & Usage and thought that this would be actually something for this site and maybe a contribution to all who might have the same confusion.
This question is about something I always get confuse with (native language German). As far as I know "did + verb" is something done and finished in the past. But isn't it the same with "verb + ed"?
The answers can be seen here english.stackexchange.com. Anything you would like to improve?